feat(analysis): worker daemon + real dispatcher + app wiring

The background analysis worker that drains analyze_page jobs:

- analysis::daemon: a lean sibling of the crawler daemon — leases only
  KIND_ANALYZE_PAGE, skip-if-done-unless-force, lease heartbeat, panic +
  timeout isolation, ack done/failed, and a failed page_analysis row on
  terminal (dead-lettered) failure. AnalyzeDispatcher trait seam.
- RealAnalyzeDispatcher: load page → storage.get → VisionClient.analyze →
  persist_analysis (skips a deleted page; caps image bytes).
- app::build spawns the daemon (own plain reqwest client) when
  ANALYSIS_ENABLED; AppHandle/main shut it down alongside the crawler.
- repo::page::find_by_id.

Tests: dispatch+ack-done, skip-when-done, force re-dispatch, terminal
failure writes failed row, panic isolation, ignores non-analyze jobs.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/src/main.rs

@@ -21,7 +21,11 @@ async fn main() -> anyhow::Result<()> {
 
     let config = mangalord::config::Config::from_env()?;
     let addr: SocketAddr = config.bind_address.parse()?;
-    let mangalord::app::AppHandle { router, daemon } = mangalord::app::build(config).await?;
+    let mangalord::app::AppHandle {
+        router,
+        daemon,
+        analysis_daemon,
+    } = mangalord::app::build(config).await?;
 
     tracing::info!(%addr, "mangalord listening");
     let listener = tokio::net::TcpListener::bind(addr).await?;
@@ -43,6 +47,17 @@ async fn main() -> anyhow::Result<()> {
             );
         }
     }
+    if let Some(a) = analysis_daemon {
+        if tokio::time::timeout(CRAWLER_SHUTDOWN_TIMEOUT, a.shutdown())
+            .await
+            .is_err()
+        {
+            tracing::warn!(
+                timeout_s = CRAWLER_SHUTDOWN_TIMEOUT.as_secs(),
+                "analysis daemon shutdown exceeded timeout; abandoning"
+            );
+        }
+    }
     Ok(())
 }